The present invention relates to a clamp used mainly for connectively fixing a flexible hose of rubber or synthetic resin, typified by a gas hose, water-service hose or the like, to the mouthpiece portion of a device, such as a cock, valve, joint or the like.
For example, when it is desired to connect a gas hose of rubber to the mouthpiece portion of a cock or joint, it is necessary to achieve a secure fixing of the hose in order to prevent the leakage of gas. When conventional clamps of the character described are classified by mechanism, the following two types may be said to be in wide use.
One of the types comprises a single metal wire wound into a pair of circular rings, and knobs of plastic material fixed to the opposite ends of the winding, the spring force of said circular rings being utilized to clamp the hose. The other type comprises a metal strip having a number of meshing apertures punched out therein, said metal strip being wound into a circular ring which functions as a worm wheel, and an operating threaded rod mounted on the circular ring and serving as a worm meshing with said meshing apertures, or comprises a metal strip wound into a circular ring, a portion of which is extended and has a nut fixed thereto, and an operating threaded rod screwed into said nut tangentially of said circular ring; in either case, the arrangement is such that the rotation of the threaded rod causes the opening diameter of the circular ring to be contractively deformed for clamping the hose.
In the former type, however, since the circular ring of wire is always in a state where its opening diameter is contracted, making it necessary to forcibly expand said opening diameter by grasping the operating knobs toward each other in using the clamp, the clamping force tends to be prematurely fatigued. Further, since the clamping force relies only on the so-called free springiness of the wire material rather than being restrained, the clamping force naturally weakens, involving much danger of the clamp idly turning or moving relative to the hose. In this connection, in order to increase the clamping force, it would be contemplated to greatly contract the opening diameter of the circular ring in advance. Such arrangement, however, would require an excessive operating force for grasping the knobs toward each other to forcibly expansively deform the opening diameter in attaching the clamp to the hose, thus detracting from the operability of the clamp.
On the other hand, with the latter mechanism, by rotating the operating threaded rod, the opening diameter of the circular ring can be smoothly expansively deformed, and since such expansive state is maintained by the threaded rod, there is no problem in the operability. On the contrary, however, because of the contractive deforming action of the circular ring brought about by the rotation of the threaded rod, coupled with the fact that a metal strip is used to form the circular ring, the clamping force lacks springiness. Moreover, hoses are made of rubber or other soft material and the final position for clamping is uncertain, so that the magnitude of the clamping force will vary with the operator's "feel", with the result that the hose can be damaged by an excessive clamping force or can idly turn or move if the clamping force is too low. Further, the need of punching out a number of meshing apertures in the metal strip required for meshing with the operating threaded rod and assembling the nut in advance makes the construction complicated and is disadvantageous to mass-production.